Scientists are warning that historic flooding could soon deluge parts of several Southern states along the lower Mississippi River, where floodwaters could persist for several weeks.
Major flooding now occurring in Nebraska, Iowa, Missouri, and other Midwestern states is a preview of what forecasters expect the rest of the spring, said Mary Erickson, deputy director of the National Weather Service.
"We expect the flooding will get worse and become more widespread," Erickson said, referring to conditions nationwide.
"The flooding this year could be worse than anything we've seen in recent years, even worse than the historic floods of 1993 and 2011," she said.
The flood threat was discussed in a conference call Thursday, as the National Oceanic and Atmospheric Administration released its 2019 spring outlook.
Flooding in Southern states this spring will be "potentially historic," NOAA said in an advisory.
Rapidly melting snow in the upper Midwest is contributing to flooding that will eventually make its way downstream to the Gulf Coast, forecasters have said.
The expected surge of water from the north is unwelcome news in parts of Mississippi. In the western part of that state, the Mississippi River is already swollen and has been flooding some communities unprotected by levees since last month.
One Mississippi region protected by levees is also flooding. That's because smaller rivers can't drain into the Mississippi River as normal because a floodgate that protects the region from even worse flooding by the big river has been closed since Feb. 15.
Around Rolling Fork, Mississippi, townspeople first noticed water rising from swamps near the Mississippi River in late February. The water eventually invaded some homes in that community, about 40 miles (65 kilometers) north of Vicksburg.
The specter of major flooding on the Mississippi River upstream from New Orleans is a more perilous situation now than in years past, some researchers believe. That's partly because the river floor has risen significantly higher over the years as sediment has collected in the river bottom, Louisiana State University hydrologist Yi-Jun Xu found.
The situation is so serious that Xu believes a "mega flood" could overpower a giant flood control structure north of New Orleans and send the Mississippi River rushing down another path entirely and creating a new route to the Gulf of Mexico. That would allow the Gulf to push saltwater upstream into the river, ruining the drinking water supply for metropolitan New Orleans, according to a summary of Xu's 2017 presentation to the American Geophysical Union.
Associated Press Writers Adrian Sainz in Memphis, Tennessee; and Jeff Amy in Jackson, Mississippi, contributed.